insight-chat: split generation system prompt into identity + procedural blocks

The framework no longer asserts "you are a personal photo memory
assistant" alongside a user-supplied custom_system_prompt — the
persona is the authoritative identity. The procedural block (tool-use
guidance, iteration budget) stays identity-free.

The user message also stops asking for "a detailed insight with a
title and summary" since the title is regenerated post-hoc anyway and
the wording was constraining voice for no data-model benefit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/insight_generator.rs

@@ -2943,6 +2943,58 @@ Return ONLY the summary, nothing else."#,
         }
     }
 
+    /// Assemble the chat system prompt from two named blocks:
+    ///
+    /// 1. **Identity / voice / format** — `custom_system_prompt` verbatim
+    ///    when supplied, or a neutral default that doesn't fight a future
+    ///    persona. The framework never asserts an identity that could
+    ///    contradict the persona.
+    /// 2. **Procedural scaffolding** — tool-use guidance, iteration budget,
+    ///    contact-filter rule. Identity-free; never asserts voice or shape.
+    ///
+    /// `owner_id_note` and `fewshot_block` are pre-rendered strings (they
+    /// already encode their own headers / blank lines). Pass empty / None
+    /// to skip.
+    pub(crate) fn build_system_content(
+        custom_system_prompt: Option<&str>,
+        owner_id_note: Option<&str>,
+        fewshot_block: &str,
+        max_iterations: usize,
+    ) -> String {
+        let identity = match custom_system_prompt {
+            Some(s) if !s.trim().is_empty() => s.trim().to_string(),
+            _ => String::from(
+                "You are reconstructing a memory from a photo. Use the gathered \
+                 context to write a thoughtful summary; you decide voice, length, and shape."
+            ),
+        };
+
+        let owner = owner_id_note.unwrap_or("");
+
+        let procedural = format!(
+            "Tool-use guidance:\n\
+             - You have a budget of {max_iterations} tool-calling iterations.\n\
+             - Call tools to gather context BEFORE writing your final answer; don't answer after one or two calls.\n\
+             - When calling get_sms_messages or search_rag, make at least one call WITHOUT a contact filter \
+               — surrounding events matter even when a contact is known.\n\
+             - Use recall_facts_for_photo + recall_entities to load any prior knowledge about subjects in the photo.\n\
+             - When you identify people / places / events / things, use store_entity + store_fact to grow the persistent memory.\n\
+             - A tool returning no results is informative; continue with the others.",
+            max_iterations = max_iterations
+        );
+
+        let mut out = identity;
+        if !owner.is_empty() {
+            out.push_str(owner);
+        }
+        out.push_str("\n\n");
+        if !fewshot_block.is_empty() {
+            out.push_str(fewshot_block);
+        }
+        out.push_str(&procedural);
+        out
+    }
+
     pub async fn generate_agentic_insight_for_photo(
         &self,
         file_path: &str,
@@ -3288,9 +3340,12 @@ Return ONLY the summary, nothing else."#,
             None
         };
 
-        // 8. Build system message
+        // 8. Build system message via the two-block helper. Custom prompt
+        // (when supplied) is the authoritative identity — the framework
+        // never appends a competing "you are a personal photo memory
+        // assistant" line. The procedural block stays identity-free.
         let owner_id_note = match owner_entity_id {
-            Some(id) => format!(
+            Some(id) => Some(format!(
                 "\n\nYour identity in the knowledge store: {name} (entity ID: {id}). \
                 When storing facts where you ({name}) are the object — for example, someone is your friend, \
                 sibling, or colleague — use subject_entity_id for the other person and set object_value to \
@@ -3298,32 +3353,16 @@ Return ONLY the summary, nothing else."#,
                 {name} directly, use {id} as the subject_entity_id.",
                 name = owner_name,
                 id = id
-            ),
-            None => String::new(),
+            )),
+            None => None,
         };
         let fewshot_block = Self::render_fewshot_examples(&fewshot_examples);
-        let base_system = format!(
-            "You are a personal photo memory assistant helping to reconstruct a memory from a photo.{owner_id_note}\n\n\
-            {fewshot_block}\
-            IMPORTANT INSTRUCTIONS:\n\
-            1. You MUST call multiple tools to gather context BEFORE writing any final insight. Do not produce a final answer after only one or two tool calls.\n\
-            2. When calling get_sms_messages and search_rag, always make at least one call WITHOUT a contact filter to capture what else was happening in {owner_name}'s life around this date — other conversations, events, and activities provide important wider context even when a specific contact is known.\n\
-            3. Use recall_facts_for_photo to load any previously stored knowledge about subjects in this photo.\n\
-            4. Use recall_entities to look up known people, places, or things that appear in this photo.\n\
-            5. When you identify people, places, events, or notable things in this photo: use store_entity to record them and store_fact to record key facts (relationships, roles, attributes). This builds a persistent memory for future insights.\n\
-            6. Only produce your final insight AFTER you have gathered context from at least 5 tool calls.\n\
-            7. If a tool returns no results, that is useful information — continue calling the remaining tools anyway.\n\
-            8. You have a hard budget of {max_iterations} tool-calling iterations before the loop ends. Plan your context gathering so you can write a complete final insight within that budget.",
-            owner_id_note = owner_id_note,
-            fewshot_block = fewshot_block,
-            owner_name = owner_name,
-            max_iterations = max_iterations
+        let system_content = Self::build_system_content(
+            custom_system_prompt.as_deref(),
+            owner_id_note.as_deref(),
+            &fewshot_block,
+            max_iterations,
         );
-        let system_content = if let Some(ref custom) = custom_system_prompt {
-            format!("{}\n\n{}", custom, base_system)
-        } else {
-            base_system.to_string()
-        };
 
         // 9. Build user message
         let gps_info = exif
@@ -3353,15 +3392,17 @@ Return ONLY the summary, nothing else."#,
             .map(|d| format!("Visual description (from local vision model):\n{}\n\n", d))
             .unwrap_or_default();
 
+        // Context-only payload — no output-shape prescription. The persona /
+        // custom_system_prompt owns voice, length, and structure. The "title
+        // and summary" claim that used to live here was unused (the title is
+        // regenerated post-hoc from the summary by generate_photo_title).
         let user_content = format!(
-            "{visual_block}Please analyze this photo and gather any relevant context from the surrounding weeks.\n\n\
-             Photo file path: {}\n\
+            "{visual_block}Photo file path: {}\n\
              Date taken: {}\n\
              {}\n\
              {}\n\
              {}\n\n\
-             Use the available tools to gather more context about this moment (messages, calendar events, location history, etc.), \
-             then write a detailed insight with a title and summary.",
+             Gather context with the available tools, then respond.",
             file_path,
             date_taken.format("%B %d, %Y"),
             contact_info,
@@ -3923,6 +3964,44 @@ mod tests {
         assert_eq!(out, "11 chars");
     }
 
+    #[test]
+    fn build_system_content_uses_custom_prompt_verbatim_for_identity() {
+        let out = InsightGenerator::build_system_content(
+            Some("You are a journal writer in first person, warm and reflective."),
+            None,
+            "",
+            6,
+        );
+        assert!(
+            out.starts_with("You are a journal writer in first person, warm and reflective."),
+            "custom prompt must lead the system content; got: {}",
+            &out[..out.len().min(200)],
+        );
+        assert!(
+            !out.contains("personal photo memory assistant"),
+            "framework identity must not leak when custom prompt is supplied"
+        );
+        assert!(out.contains("Tool-use guidance"));
+        assert!(out.contains("budget of 6"));
+    }
+
+    #[test]
+    fn build_system_content_uses_neutral_default_when_no_custom() {
+        let out = InsightGenerator::build_system_content(None, None, "", 6);
+        assert!(out.contains("reconstructing a memory from a photo"));
+        assert!(!out.contains("personal photo memory assistant"));
+        assert!(out.contains("Tool-use guidance"));
+    }
+
+    #[test]
+    fn build_system_content_includes_fewshot_and_owner_id() {
+        let owner = "\n\nYour identity in the knowledge store: Alice (entity ID: 7).";
+        let fewshot = "## Examples\n\n### Example 1\n...\n\n---\n\n";
+        let out = InsightGenerator::build_system_content(None, Some(owner), fewshot, 6);
+        assert!(out.contains("Alice (entity ID: 7)"));
+        assert!(out.contains("## Examples"));
+    }
+
     #[test]
     fn render_fewshot_empty_returns_empty_string() {
         assert!(InsightGenerator::render_fewshot_examples(&[]).is_empty());